1. Field of the Invention
The present invention relates broadly to the manufacture of float glass and, more particularly, to improved means for mounting heat exchangers which extend through the side walls of float glass apparatus.
2. Description of the Prior Art
As is well known, manufacture of flat glass by the float process involves delivering molten glass at a controlled rate onto a bath of molten metal which has a greater density than that of glass (such as tin or alloys of tin, for example) and advancing it along the surface of the bath under physical and thermal conditions which assure that a layer of molten glass will be established on the bath, that from the layer there will develop a buoyant body of molten glass of stable thickness, and the buoyant body in ribbon form will be continuously advanced along the bath and sufficiently cooled as it advances to permit it to be removed from the bath by mechanical conveying means.
Over the bath of molten metal there is provided an enclosed head space or plenum chamber to contain a protective , so-called float atmosphere. This atmosphere is generally comprised of non-oxidizing or reducing gas or gases (usually a mixture of gases such as nitrogen and hydrogen) maintained under sufficient pressure to prevent contamination by infiltration of external atmosphere.
Various devices such as coolers, heaters, water fences, edge rolls, top assistors and linear induction motors are inserted through the side walls of the bath structure to control conditions as the glass moves over the metal bath and assure that a ribbon having the desired characteristics will ultimately be produced. Although it may obviously have general utility in the supporting of various elongated devices, the present invention is particularly adapted for the installation and support of heat exchangers, and particularly coolers, extending over the ribbon upon the molten metal bath of a float glass producing facility, and will be so described herein.
The aforementioned regulating devices, including overhead coolers, are generally supported upon the floor adjacent the bath structure, or by the lower bath structure itself, and connected to various utility service lines outside the bath structure, so that the limited area along side the bath structure often becomes quite congested. In order to vary the heat exchange pattern and achieve the overall temperature pattern desired for production of different compositions and thicknesses of glass, it becomes necessary to periodically install or remove overhead heat exchangers at selected locations along the bath structure. Such exchangers heretofore have generally been of the flat, tubular multipass type which extend transversely across the bath structure and are supported at each end outside the enclosed plenum chamber as by brackets affixed to the structural framework of the bath. They are of considerable length, on the order of twenty feet, and quite heavy so that installation and/or removal requires the services of two or more workers. The exchanger is inserted from one side so as to extend partially across the bath chamber, and its leading end is then engaged from the opposite side by a worker using a hook who then supports and guides the leading end as the exchanger is moved into position. The exchanger is positioned a short distance above the surface of the molten metal bath so that the hook, or even the exchanger itself, may accidentally come in contact with the glass ribbon during the installation or removal, resulting in damage to, if not complete severing of, the ribbon.
One proposal for providing flexibility in the heat exchange pattern on float glass apparatus is set forth in U.S. Pat. No. 3,333,936 to Warren, which discloses overhead heat exchangers having partially insulated surfaces. The heat exchangers are mounted at their ends so as to be selectively rotatable about their longitudinal axes, whereby the rate of heat exchange with the glass may be varied by changing the angular positions of the devices. Another such system is shown in U.S. Pat. No. 3,649,237, issued Mar. 14, 1972, to Classen et al. As disclosed therein, pairs of offset cooling elements extend inwardly from each side of the chamber containing the bath of molten metal. Adjustable roller stands are provided on the floor alongside the bath structure for supporting the coolers from below, and an additional roller mounted above maintains the cooler in engagement with the roller stands. Drive means are provided for moving the coolers inwardly or outwardly along their longitudinal axes in response to observed temperatures of the glass ribbon for varying the heat exchange pattern.